Brendan Rodgers watched on from the touchline as his side earned a fourth trophy since the former Liverpool manager took over back in the summer of 2016, thanks to goals from Forrest and a Moussa Dembele penalty.
The 26-year-old opened the scoring at Hampden Park in emphatic style, after good work from Callum McGregor saw Forrest receive the ball from his Scotland teammate before curling a left-effort into the far corner.
His second-half strike gave Celtic the lead before Dembele doubled the margin from the spot, but it was not all plain sailing as goalkeeper Craig Gordon produced a marvellous stop to keep out Well goal machine Louis Moult.
Watt, who now plays his football for Belgian side OH Leuven, claimed that Forrest is Celtic's "best player" when fit and confident, despite the presence of players such as Dembele, Kieran Tierney and Scott Brown.
Frightening mate! Always said keep him fit and if he’s confident he’s best player in that team https://t.co/daCvHJlDEH— Tony Watt (@Tony_Watt7) November 26, 2017
Forrest has been in exceptional form for Celtic this season, as he kept fit-again Man City loanee Patrick Roberts on the substitutes bench from the off before the two swapped in the 78th minute.
Scoring eight goals this season, Celtic's number 49 has found the back of the net in crucial Champions League qualifiers against Rosenborg and FC Astana as well as laying on two assists for his side.